In the xerographic process of producing copies, an image is created upon a photoconductive surface by first placing a uniform electrostatic charge on the photoconductive surface and then exposing such charged surface to light so as to create a desired image thereon. In the standard xerographic copying technique, light is reflected from the background or non-printed portion of a document to be reproduced and the text or printed portion of the document will appear on the photoconductive surface as an image of charged areas surrounded by a substantially neutral background. This image is then developed by contacting such image with a toner or development powder charged with a polarity opposite to that of the image charge. This toner is placed into contact with the photoconductive surface at a development station either through a cascading device or a magnetic brush unit. The toner particles on the now developed image are then transferred to a sheet upon which the transferred image is subsequently fused. Unfortunately, the transfer of toner is not completely efficient, resulting in a residual deposit of finely divided toner particles remaining on the photoconductive surface. Before the photoconductive surface can be used in another copy cycle, it is necessary that this residual toner be removed without harmful effect to the photoconductive surface otherwise ghosting will begin to show up on subsequent copies resulting in poor copy quality. Ghosting is the reproducing of post images of prior document reproduction which results from failure to clean the photoconductive surface after transfer takes place.
In the past, different systems have been used for the purpose of cleaning residual toner from a photoconductive surface. Some schemes involved cascading a cleaning powder onto the photoconductive surface following the transfer step so as to carry away the residual toner. The most common cleaning system is a mechanical rotating brush using a material such as fur or felt bristles in combination with a vacuum cleaner collector that would carry away the particles removed by the brush. Another method used a magnetic brush unit to remove residual toner in combination with a cascading development station. Still another system involved the use of a magnetic brush unit which would first develop an image and then the machine would go through a second cycle during which the magnetic brush unit would act as a cleaning station. In all of these prior schemes for removing residual toner from a photoconductive surface a cleaning station was provided that removed the residual toner or a second cycle was necessary to accomplish the cleaning function.